Networks for transmitting audio and video information in digital form are being developed. To transmit audio or video information for viewing or listening, the data must be transmitted in real time.
IEEE 1394 was proposed as a standard for networks realizing such realtime data transmission, and is widely used today. IEEE 1394 is mounted as an external interface in many digital video/audio apparatuses including home digital VCRs. In VCRs, the use of IEEE 1394 has made it possible to control the VCR from an external device and also to transmit data from an external device to the VCR for recording or reproduction.
In PCs, on the other hand, with advances in multimedia technology and the advent of recording media such as large-capacity hard disks and magneto-optical disks, it has become possible to process video and audio information as well. That is, PCs can now have the capability to function as a recording and reproduction apparatus or a monitor for video and audio information. Windows 98, the standard OS for PCs, for example, supports IEEE 1394, making it possible to transfer AV data between PCs and digital video/audio apparatuses such as VCRs. It is expected that the fusion between PCs and digital video/audio apparatuses will further advance in the future.
For a PC to be able to handle video and audio information, application software for processing video and audio information must be installed on the PC. AV data transferred from a video/audio apparatus is input into the PC, and processed for display, recording, reproduction, etc. by the application software installed on the PC. For example, if the application software is one that has a recording function, the AV data transferred from the video/audio apparatus is input into the PC, and recorded on a recording medium such as a hard disk or a magneto-optical disk by the application software. Application software capable of processing AV data thus provides a variety of capabilities and, by installing such application software, a variety of AV data processing functions such as recording, reproduction, display, and manipulation can be added to the PC.
Some AV data claim copyright protection, for example, by prohibiting copying or by permitting copying only once. In digital video/audio apparatuses such as VCRs, such copyright claimed AV data is recorded or played back by respecting the claimed copyright protection status. For example, for AV data for which copying is prohibited, VCRs do not record the data. On the other hand, for AV data for which copying is permitted only once, VCRs are allowed to record the data. Whether copying of AV data is permitted or not is confirmed by exchanging authentication or usage approval information based on copyright between the VCR and the AV data transmitting apparatus such as an STB (satellite broadcast receiver).
In today's PCs, however, if one wishes to respect the claimed copyright of copyright claimed AV data, since a variety of functions, such as recording, reproduction, and display, can be incorporated into a PC by utilizing the functions of the application software installed on the PC, there arises the problem that once the copyright claimed AV data is passed to the application software, one can freely process the AV data for recording, etc. by using the application software, defeating the purpose of the copyright protection.
Even if a mechanism is devised to append a license for processing copyright claimed AV data to application software, the copyright may not be able to be protected if the application software is illegally modified. In that case, if a tamper resistant system is built into the application software to prevent illegal modification of the application software, the copyright can be protected effectively. However, this method is not without problems; that is, once the tamper resistant system is broken by an illegal-minded user, substantial changes would have to be made not only to the organization of the PC but also to the structures of the OS, the application software, etc. resulting in a large loss.
Furthermore, if copyright claimed data is illegally handled using application software to which a license as described above is not granted, it is not possible to identify the source application software from the data that was illegally copied by the application software and distributed. That is, even if the presence of illegal application software is known, it is not possible to detect and disable the use of the illegal application software. That is, the problem is that it is not possible to identify and eliminate illegal software for copyright protection purposes.
One characteristic of illegal usage by software is that the method of illegal usage can be distributed widely at low cost by just copying the software. This leads to the problem that even if the source of the illegal distribution can be identified, it is not effective to employ a method applied in the case of hardware that disables the use by illegal apparatuses on an apparatus by apparatus basis. For example, when copies of an illegally altered application capable of escaping the check by a tamper resistant system are distributed, or when a method of escaping the check by a tamper resistant system is discovered and distributed, with the prior known method of disabling the use for each individual computer it is not possible to prevent such illegal act; besides, it could disable the use of legitimate applications.
In view of the above situation, it is apparent that once an illegal distribution by a computer modified for the purpose of illegal distribution is discovered, since measures have to be taken to prohibit the use of AV data on computers or on the OS and to modify the computers or the OS itself, the damage is extensive and the cost involved is very high.
As described above, the problem is that there are no effective ways to prevent illegal use once copyright claimed data is illegally distributed.